Lubricating composition



United States Patent of Delaware No Drawing. Filed June 8, 1965, Ser.No. 462,435

14 Claims. (Cl. 252-47.5)

This invention relates to a lubricating composition designed for thelubrication of turbine engines which operate over a wide temperaturerange and under severe operating conditions. More particularly, thisinvention relates to a synthetic lubricating oil composition having goodextreme pressure and superior non-corrosive properties.

Synthetic base lubricants of the ester-base type have been found to bevery useful in meeting requirements for the lubrication of modern highperformance turboprop, turbojet and turbofan engines. However, eventhese superior base components must be tailored to meet certainstringent engine performance requirements as set forth in appropriatespecifications by the military and by commercial aircraft enginemanufacturers. It is particularly difiicult to achieve a synthetic oilcomposition having all the desired properties to withstand extremethermal and oxidative stress without becoming corrosive due to excessiveoxidation of the components of the synthetic oil.

Dimerized fatty acids and mixtures of same containing trimer acidmaterial have heretofore been employed to impart load carryingproperties to synthetic lubricant compositions, see US. 3,048,542.Unfortunately, compounded synthetic lubricating oils containing dimeracids and their mixtures containing trimer acids material even in minuteproportions tend to promote corrosion of copper, magnesium and lead withthe result that synthetic lubricating oils containing same cannot meetthe anti-corrosion specifications required for current syntheticlubricants. A synthetic lubricating oil composition has now beendiscovered which has superior non-c0rrosive properties while retaining ahigh level of load-carrying properties. When employed in a fullycompounded oil, the resulting synthetic lubricating oil compositionmeets the severest performance requirements of todays jet engines.

The lubricating composition of this invention broadly comprises anester-type fluid having lubricating properties containing a monoamide ofan heterocyclic aromatic amine and a material consisting essentially oftrimer acids produced by the condensation of unsaturated monocarboxylicacids having between 12 and 22 carbon atoms per molecule in an amountsufficient to impart excellent extreme pressure properties to thecomposition as well as superior anti-corrosion properties in acompounded oil. Generally, the monoamide is employed in an amountranging from about 0.01 to 1.0 weight percent based on the weight of thelubricating oil composition.

The compounded lubricating oil composition will contain an oxidationinhibiting amount of an heterocyclic sulfur and nitrogen containingcompound from the group consisting of orthothiazine, metathiazine,parathiazine, phenothiazine and their low molecular weight aliphaticderivatives, an oxidation inhibiting amount of an aromatic amine fromthe group consisting of naphthylamine, diphenylamine, phenylene diamineand their low molecular weight aliphatic and aromatic derivatives and acor- "ice rosion inhibiting amount of a compound from the groupconsisting of quinizarin, alizarin, purpurxanthrene, anthrarufin andchrysazin. The compounded oil is still further improved with a corrosioninhibiting amount of sebacic acid. It is conventional to employ aviscosity index improving amount of an alkylrnethacrylate polymer in thelubricating oil. Dispersant type methac-rylate copolymers, such as thoseprepared from alkylmethacrylate and nitrogen containing vinyl monomers,are also advantageous. The low molecular weight aliphatic derivativesreferred to above are those having from 1 to 8 carbon atoms in the alkylradical and the low molecular weight aromatic derivatives are thosehaving 6 carbon atoms in the aryl radical of the derivative.

The novel extreme pressure and loadcarrying additive of this inventionis a monoamide of a polymerized polybasic acid. More particularly, thisadditive is a monoamide of an heterocyclic aromatic amine and a materialconsisting essentially of trimer acids produced by the condensation ofunsaturated monocarboxylic acids having between 12 and 22 carbon atomsper molecule.

The heterocyclic aromatic amines from which the monoamide is preparedinclude the aminopyridines, dipyridylamines and the phenothiazines.Specific effective heterocyclic aromatic amines are Z-aminopyridine, 3-aminopyridine, 4-aminopyridine, 2,2'-dipyridylamine, 3,3-dipyridylamine, 4,4-dipyridylamine and phenothiazine.

Trimer acids are fatty materials produced by subjecting unsaturatedfatty acids having between 12 and 22 carbon atoms per molecule,preferably about 18 carbon atoms, to condensation by moderate steampressures of from to 300 p.s.i.g. at temperatures from 260 to 360 C. fora period of from about 3 to 8 hours. Processes for forming these acidsare set forth in such patents as US. 2,482,761, 2,631,979 and 2,632,695.Another method for preparing the trimer acid mate-rials broadlycomprises heating a short chain aliphatic alcohol ester of a diethylenicfatty acid at about 300 C. for several hours in an inert atmosphere. Theresulting polymerized esters containing trimer acid material are thenseparated by distillation and hydrolyzed with hydrochloric acid or itsequivalent. Fatty oils have also been heat polymerized and thereafterhydrolyzed to produce the polymer acids. The trimer acid is readilyseparated by distillation or by a solvent extraction process from themonomeric, dimeric and higher polymeric materials usually co-produced inthe foregoing methods.

The trimer acids used in the present invention, although preferablyconjugation products of three of the same molecules which are diorpolyethylenic, are also products of the combination of monoethyleniccompounds and polyethylenic compounds, for instance, linoleic acid andoleic acid trimerizer to become the trimer of linoleic and oleic acids.It is essential to have at least one polyethylenic compound present inorder to form the trimer acid.

Specific fatty acids useful for preparing trimer acid from the class ofethylenic carboxylic acids having from 12 to 22 carbon atoms include4-dodecenoic, 5,9-dimethyl- 2,8-decadienoic, myristoleic, palmitoleic,oleic, linoleic, linolenic and erucic acid. The preferred acid islinoleic acid on the basis of availability from which is produced thepreferred trimers of linoleic acid. These particular trimer acids areproducer commercially under the name Emery 3162D by Emery Industries.All of the above acids are generally obtainable by hydrolyzing vegetableoils, such as linseed oil, soy bean oil, cotton seed oil, and peanutoil.

One method for preparing the monoamide is by reacting equivalent moleratios of trimer acid and the heterocyclic aromatic amine. Since trimeracid is tribasic and the noted amines are monofunctional with respect toamide formation, the proportions indicated produce primarily themonoamide. The two compounds are reacted by refluxing in xylene so as tomaintain a reaction temperature of about 380 to 390 F. while the waterformed is removed during the reaction. When the reaction is complete,the xylene is stripped off under reduced pressure. Specific examples ofthe preparation of monoa-mides of this invention are given below:

Example 1 36 g. (0.3 mole) of thionyl chloride was added slowly to 96 g.of a mixture of polymerized linoleic acid containing 48 percent of thetrimer of linoleic acid. Upon completion of the addition, 100 ml. oftoluene was added and the mixture heated at reflux temperature for 45minutes to drive off volatile reaction products. 32 g. (0.16 mole)phenothiazine was dissolved in 300 ml. toluene in a second vessel. Thereaction product of the acid and thionyl chloride was added slowly withstirring and the mixture heated to reflux temperature. The solvent andvolatile materials were evaporated under vacuum at 140 F. in a rotaryevaporator. The crude reaction product was dissolved in toluene, treatedwith 20 g. activated charcoal, filtered and stripped at 200 F. and apressure of 16 mm. of mercury absolute. The resulting 98 g. of the amideof phenothiazine was identified through infrared absorption.

Example 2 420 grams of the trimer acid of linoleic acid, Emery 3162D(1.5 equivalents) and 47 grams of Z-aminopyridine (0.5 equivalent) wererefluxed in xylene for 24 hours at 370 F. and 9.5 ml. of water was takenoff. The product was then stripped at 400 F. under mm. of pressure. Therecovered monoamide of trimer acid and 2-aminopyridine had a Total AcidNo. of 112 and was found to contain 2.9% N as compared to a theoreticalcomposition of 3.07% N.

Example 3 840 grams of the trimer acid of linoleic acid (3.0equivalents) and 94 grams of Z-aminopyridine (1.0 equivalent) wererefluxed in xylene for 19' hours at 387 F. and 19.5 ml. of water wastaken off. The product was stripped at 400 F. under 15 mm. of pressure.The recovered monoamide of trimer acid and Z-aminopyridine had a TotalAcid No. of 116 and was found to contain 3.0% N as compared to thetheoretical N content of 3.07%.

The foregoing novel E.P. agents are employed in the lubricating oilcompositions in concentrations ranging from about 0.01 to 1.0 weightpercent. The preferred amounts of the BF. agents are from about 0.05 to0.2 weight percent.

Phenothiazine is a preferred primary anti-oxidant and anti-corrosiveagent for lubricating oils having the formula:

Other effective anti-oxidants of this class include orthothiazine,metathiazine and parathiazine. They inhibit corrosion by preventingoxidation of components of the lubricating composition to acidic bodieswhich are inherently corrosive. The thiazine compound is generallyemployed in a concentration of 0.1 to 2 weight percent of the lubricantcomposition with the preferred amount being from about 0.4 to 1.5percent.

An amine from the class of aromatic amines having anti-oxidant orantiozonant properties is also employed in the fully compoundedlubricating oil composition. These aromatic amines are naphthyla-mine,diphenylamine, phenylene diamine and their C to C alkyl and C arylderivatives. Particularly effective aromatic amine antioxidants aredioctyldiphenylamine and phenyl-l-naphthylamine. Other effectivearomatic amines include N- phenyl-p-phenylene diamine,N,N'-diphenyl-p-phenylene diamine, N,N' -bis-(octylphenyl)-p-phenylenediamine, p-hydroxydip-henylamine and its esters,N-phenyl-N-isopropyl-p-phenylene diamine, N,N'-dioctyl-p-phenylenediamine. The amines are employed in amounts ranging from about 0.1 toabout 4.0 percent by weight of the lubricant composition with thepreferred proportions ranging from about 0.5 to 3 percent.

Another class of anti-oxidant and anti-corrosive agents a member ofwhich is employed in the finished lubricating oil composition includesquinizarin, alizarin, purpurxanthrene, anthrarufin and chrysazin. Thepreferred agent, quinizarin, has the formula:

A member of this class is particularly effective to enhance low coppercorrosion properties in the lubricating composition. These componentsare effective in a relatively small concentration ranging from about0.01 to 0.5 percent with the preferred range being from about 0.05 to0.2 percent.

Sebacic acid is a useful corrosion inhibiting additive which isadvantageously employed in the lubricating oil of this invention.Sebacic acid imparts substantially improved corrosion resistance to thelubricants particularly with respect to the metal, lead. Sebacic acidimparts this property in surprisingly small concentrations in thelubricant ranging from about 0.0001 to 0.1 percent and preferably from0.001 to 0.05 percent.

Methacrylate polymers are well known V.I. improvers and por pointdepressors. Polyester base luubricants, al-

though they, per se, possess excellent V.I. and pour, often require thepresence of small concentrations of methacrylate polymers to improvedispersancy and meet the requirements of military specifications. Thesemethacrylate polymers are usually copolymers of two or more esters ofmethacrylic acid and usually have a molecular weight between 5000 and20,000. The met'hacrylate esters have the following general formula:

wherein R is an aliphatic radical preferably ranging from butyl tostearyl.

Copolymers which find particular use as V.I. improvers and pour pointdepressants are the following: a copolymer wherein R in the aboveformula comprises 20% lauryl, 40% octyl and 40% 'cetyl; a copolymerwherein R in the above formula is 50% stearyl and 50% lau1yl; a copolymer wherein R in the above formula comprises 50% lauryl and 50% octyl.

Methacrylate polymers are usually sold in the form of a concentratecomprising approximately 20 to 50% polymer in a carrier oil. For thelubricant compositions of this invention, it has been found advisable touse an ester-type carrier oil, such as dioctylsebacate ortrimethylolpropane tripelargonate, rather than the usual mineral baselubricating oil. The use of a methacrylate ester in an ester-typebarrier oil has proven particularly effective in meeting the lowtemperature and viscosity requirements of military specifications.Dispersant type methacrylate copolymers, for example Acryloid HF-866manufactured by Rohm and Haas, containing nitrogen func tional groups,such as vinylpyrrolidone and dimethylaminoethylmethacrylate areparticularly elfective and are described in U.S. Patents 3,142,664,3,147,222 and 3,153,- 640. Methacrylate polymers can constitute 0.1 to20 weight percent of the composition but ordinarily are used in aconcentration between 0.25 and weight percent.

A commonly used ester base lubricant is an aliphatic diester of anorganic dicarboxylic acid. The dicarboxylic acid component is usually analiphatic dicarboxylic acid containing 6 to 12 carbon atoms but glutaricacid esters and succinic acid esters may also be used. From thestandpoint of cost and availability, the preferred dibasic acids areadipic acid, sebacic acid and azeloic acid. The aliphatic alcohols use-dto form the diesters usually contain at least 4 carbon atoms and maycontain 20 or more carbon atoms although C to C alcohols are preferred.Ether alcohols, such as Cellosolve, Butyl Cellosolve and Carbitol mayalso be used in the formation of the allphatic diesters of organicdicarboxylic acids used as the lubricating base in the compositions ofthis invention.

Specific examples of the dialkyl esters of aliphatic dicarboxylic acidsare as follows: di-isooctyl azelate, di-2- ethylhexyl sebacate,di-Z-ethylhexyl azelate, di-2-ethylhexyl adipate, dilauryl azelate,di-sec-amyl sebacate, di-2- ethylhexyl alkenylsuccinate,di-2-ethoxyethyl sebacate, di- 2-(2'-methoxyethyoxy) ethyl sebacate,di-2-(2'-ethylbutoxy) ethyl sebacate, di-2-butoxyethyl azelate, di-2-(2-butoxyethoxy) ethyl alkenylsuccinate, etc.

In addition to the aliphatic dicarboxylic acid esters described above,polyester and complex ester lubricants formed by a reaction of analiphatic dicarboxylic acid, a glycol and a monofunctional compound,which is either an aliphatic monohydroxy alcohol or an aliphaticmonocarboxylic acid, in specified mole ratios are also employed as thesynthetic lubricating base in the compositions of this invention;polyesters of this type are described in U.S. 2,628,974, Complex estersformed by reaction of a mixture containing specified amounts of2-ethyl-1,3- hexanediol, sebacic acid and 2-ethylhexanol and by reactionof a mixture containing adipic acid, diethylene glycol andZ-ethylhexanoic acid illustrate this class of synthetic polyesterlubricating bases.

Polyesters formed by reaction of a monocarboxylic acid and a glycol orpolyol may also be used as the ester component. The acid component isusually an aliphatic acid containing 3 to 20 carbon atoms and preferably4 to 10 carbon atoms. The glycol or polyol component is advantageously astraight glycol, such as 1,5-hexanediol, but ether glycols, such astetraethylene glycol, may also be used. Sterically hindered neopentyltype glycols, such as 2-methyl, 2-ethyl, 1-3, propanediol, are favoredfor enhanced thermal stability.

Specific examples of the diesters of glycols are the following:di-n-decanoate of 1,4-butanediol, di-Z-ethylhexanoate of 1,6-hexanediol,dilaurate of 1,4-hexanediol, dioctanoate of 1,5-pentanediol, dilaurateof tetraethylene glycol, dilaurate of triethylene glycol, dioctanoate ofpentaethylene glycol. Examples of triesters are trimethylolpropanetriheptanoate, trioctanoate and tripelargonate. Examples of tetraestersare pentaerythritol tetracaproate and pentaerythritol anddipentaerythritol esters with mixtures of aliphatic acids containingthree to ten carbon atoms.

Complex esters formed by reacting trimethylol and tetramethylol alkaneswith various mole ratios of dibasic acids and monobasic acids oralcohols are other examples of polyesters useful for the base fluid ofthe lubricants of this invention. Pentaerythritol tetraesters of Caliphatic carboxylic acid are a preferred class of polyester lubricatingoils.

The sulfur analogs of the above-described esters are also used in theformulation of the lubricating compositions of this invention.Dithioesters are exemplified by di-Z-ethylhexylthiosebacate, di-n-octylthioadipate and the dilaurate of 1,5-pentanedithiol; sulfur analogs ofpolyesters are exemplified by the reaction product of adipic acid,thioglycol and 2-ethylhexyl mercaptan.

Other additive components can be advantageously incorporated in thelubricant composition of the invention. For example, an anti-foam agentsuch as a hydrocarbon or kerosine concentrate of dimethyl silicone in anamount ranging from about 0.0001 to 0.01 percent by weight is generallyadded to the lubricating oil. Detergents, such as the metal salts ofphenates and sulfonates, are also widely used dispersants. Inparticular, barium sulfonates have been found useful since they inhibitcorrosion and rusting.

The lubricating composition of the invention was tested for itsanti-corrosive, and ER properties in a 400 or 425 F. Oxidation-CorrosionTest, a Lead Washing Test, an SOD Lead Corrosion Test and in the RyderGear Test.

The 425 F. Oxidation and Corrosion Test is conduct ed in accordance withMethod 5308.4 of Federal Test Method Standard No. 791a (issued Dec. 31,1961) except for the following modifications to conform to Pratt &Whitney Aircraft Specification 5213 (Type II). The bath temperature ismaintained at 425 F. plus or minus 1 F. instead of at 250 F. This testis conducted for a period of 48 hours instead of 168 hours specified inthe original test. Copper corrosion, as evidenced by a weight change ofgreater than $0.30 mg./cm. Cu, is considered a failure and cause forrejection.

The Lead Washing Test is a method intended for the determination of thetendency of a jet engine oil to remove lead flashing from ball bearingcages and/or to attack silver plating beneath the lead. Ratings in thistest correlate with airline service experience and with theTexaco-United Airlines Jet Engine Simulator Test using bearings, gearsand seals from a Pratt and Whitney 1T3 C-6 model engine. This test isrun with a sample of 800 mls. with 3 liters of oxygen per hour beingbubbled into the sample. The sample is agitated with a stainless steelstirrer at 300 r.p.m. Lead and silver test panels are introduced. Thistest is usually run for a l68-hour period. At the termination of thetest, the metal panels are Weighed after naphtha Washing and air dryingand then weighed again after rinsing and Wiping withorthodichlorobenzene, rinsing with a 50-50 volume mixture of acetone andASTM precipitation naphtha followed by air drying.

Outline 0 procedure (1) A stirrer is prepared by cutting an 18 gage(0.0500) stainless steel disc 1 /4 in diameter into 4 segments with thecuts extending to Within A" of the center. The segments then formed arebent to 30 to form a four-bladed propeller. The propeller is thenmounted on a A" diameter stainless steel shaft approximately 9 /2" long.

(2) One lead panel is prepared from a four pound lead sheet" 4 thick)conforming to ASTM B 29-55 Chemical Lead grade. The panel is by 1%" by1%" and has a diameter hole in the center.

One silver panel is prepared from soft fine electrolytic silver sheetapproximately 0.030 inch thick. The panel is 1 inch square and has a /sinch diameter hole in the center.

(3) Clean the lead and silver test panels by rubbing with No. steel woolto produce a uniform bright finish over the entire surface of the facesand edges of each panel. Swab panels with a clean cotton pad wetted withprecipitation naphtha, rinse with fresh naphtha and air dry. (Note: Thepanels are not to be touched with bare hands after the start of thecleaning operation.) Weigh each panel to the nearest 0.1 milligram andrecord the weights.

(4) Place a 1,000 ml. tall form beaker containing 800 ml. of test oilinto a bath preheated to 250 F. so that the test oil level is at least1" below that of the bath oil.

(5) Hang the lead and the silver panels midway in the oil at oppositesides of the beaker. Insert the stirrer to within /2" of the bottom ofthe breaker and by suitable means rotate it at 3003125 rpm.

(6) After the specified test period the metal panels are removed fromthe test oil.

(7) Rinse panels in a 50/50 volume mixture of ASTM precipitation naphthaand acetone, air dry and weigh to the nearest 0.1 milligram. This is therinsed Weight.

(8) With a cotton swab soaked in 50/50 naphtha/acetone, wipe off most ofany deposit from the panels. Wipe panels again with a cotton swab soakedin orthodichlorobenzene attempting to wipe off any deposit remaining.Wipe panels again with a fresh cotton swab soaked in 50/ 50 naphtha/acetone followed by a rinse in fresh 5 0/ 50 naphtha/acetone, air dryand weigh. This is the wiped weight. Lead corrosion evidenced by aweight change greater than $6.0 mg./in. determined either before orafter wiping, fails to pass this Lead Washing Test.

The SOD Lead Corrosion Test which is described in militaryspecifications, MIL L-7808C, Lubricating Oil, Aircraft Turbine Oil,Synthetic Base, dated Nov. 2, 1955, was used to determine the corrosionresistance of lubricating oil compositions of the invention.

The SOD Lead Corrosion Test consists of exposing a lead specimen to theaction of a test lubricant for one hour at 325 F.- :2 F. in the presenceof a copper catalyst. The test lubricant is mechanically stirred andfiltered dry air is introduced into the test lubricant at a controlledrate. Results are presented as change in weight (mgs.) per square inchof lead specimen surface area.

The Ryder Gear Test which is intended for the evaluation of ascuff-limited load-carrying ability of those lubricants used inreduction and accessory drives of turbojet and turboprop engines isdescribed in US. 3,048,542.

Base Fluid A employed in the examples below is pentaerythritoltetracaproate. It is prepared from purified pentaerythritol and amixture of C monobiasic acids. This base fluid has the followingproperties:

Viscosity, cs. at 210 F. 4.59 Viscosity, cs. at 100 F. 21.3 Viscosity,cs. at 40 F. 4788 Viscosity index 129 Flash, F. 490

This fluid has an 131 value of 1710 lb./in. as determined by the RyderGear Test.

Base Fluid B is technical grade pentaerythritol esterified with amixture of 38 percent valeric, 13% Z-Inethylpentanoic, 32% octanoic and17% pelargonic acids. This base fluid has the following properties:

Viscosity, cs. at 210 F 4.93 Viscosity, cs. at 100 F 25.6 Viscosity, cs.at 40 F 7023 Viscosity index 131 Flash, F 490 Ryder Gear, lb./in 2040 8Base Fluid C is purified pentaerythritol esterified with a mixture of 1percent butyric acid, 92 percent valeric acid, 4 percent caprylic acid,1 percent pelargonic acid and 2 percent capric acid. This base fluid hasthe following properties:

Viscosity, cs. at 210 F 3.80 Viscosity, cs. at 100 F 17.62 Viscosity,cs. at 40 F 34.38 Viscosity, cs. at 64 F. (extrapolated) 21,000 Pour, F75 Melting range of frozen oil, F -30 to -15 Ryder Gear, p.p.i 1305Ryder Gear, relative percent 47 Base Fluid D is trimethylolpropaneesterified with a monobasic acid mixture consisting of 2% valeric, 9%caproic, 13% heptanoic, 7% branched chain octanoic,

3% capryllic, 65% pelargonic and 1% capric acids. This base fluid hasthe following properties:

Viscosity, cs. 210 F 4.29 Viscosity, cs. at 100 F 19.98 Viscosity, cs.at 40 F 3638 Pour, F 75 Cloud, F Flash, F. 480 Fire, F. 545 Evaporation,percent, 6 /2 hr./400 F 4 Ryder Gear Test, lb./in. 2420 Ryder Gear Test,relative rating, percent 88 Base Fluid E is trimethylolpropanetripheptanoate and has the following properties:

Viscosity, cs. at 210 F 3.46 Viscosity, cs. at 100 F 15.8 Viscosity, cs.at 65 F 14,900 Flash, F 90 Flash, F 460 Fire, F 520 Evaporation,percent, 6 /2 hr./400 F 6 Base Fluid F is his (Z-ethylhexyl) sebacate,having the following properties:

Viscosity, cs. at 210 F 3.34 Viscosity, cs. at F 12.91 Viscosity, cs. at-40 F 1470 Viscosity, cs. at 65 F 8583 Pour, F 75 Cloud, F 80 Flash, F445 Fire, F 500 Evaporation, percent, 6 /2 hr./400 F 18 Ryder Gear Test,lb./in 1960 Ryder Gear Test, relative rating, percent 77 Base Fluid G ishis (tridecyl)sebacate.

Base Fluid H is his (2,2,4-trimethylpentyl) azelate.

The composition of the ester base lubricating compositions and theircorrosion and BF. properties are given in the tables below. The amountsof the additive components in the lubricating compositions are given aspercent by weight. Acryloid A consists of butyl, lauryl and stearylmethacrylate vinylpyrrolidone copolymer in trimethylpropane triester ascarrier (50% active polymer). Acryloid B consists of a higher molecularweight version of Acryloid A in the same carrier (30% active polymer).Acryloid HF866 is a dispersant type polymer in dioctyl sebacate solutionmanufactured by Rohm and Haas.

Acryloid C is the same as Acryloid A except that the carrier is BaseFluid F.

TABLE I Lubricating Oil Blend Blend A Blend Blend D Blend E amideSebacic Acid.. Quinizarim.

Dimer Acid (Empol 1 0.05 0.05 Antifoam concentrate (10% si icone),

p.p.m 100 100 100 100 100 Tests:

Kin Vis, 100 F., cs 26.1 25.8 26. 4 28. 5 28. 5 TAN, mg. KOH/g 0.12 0.28 0.11 0.19 0.24 Ryder Gear Test, 1b./1n 2730 2585 2570 2710 425 FOxid-Cort Test, 48 h 100 F. Vis. Inc, percent 30. 3 25 40 41 39. 4 TAN,mg. KOH g 2.0 2.16 1.86 1.34 1163 Metal wt. Change, mg./cn1. Cu 0.40 -0.21 1.48 -0. 43 0. 29 Lead Washing Test, 250 F.:

Duration, hrs 168 168 168 168 336 Pb Wt. Change- Before wiping, mgJin.+41. 0 +0. 5 +9. 6 +0. 4 +0. 26 After Wiping, mg./in. +40. 0 +0. 2 1. 1-1. 2 -0. G SOD Lead Corrosion, mgJin. 5. 5 -1.0 +0.8 0 4 LubricatingOil Blend Blend F Blend G Blend H Composition wt. percent:

Base Fluid B Acryloid (HF-866).. Phenothiazine Dioetyldiphenyl amine.ZAmino-Pyridine Amide of trimer acid Phenothiazine amide of trimer acid-Quinizarin.

Scbacic acid Antifoam concentrate (10% Tests:

Appearance Kin Vis at 100 F. cs. Kin Vis at 210 F TAN, mg KOH/gOxid-Corr. Test Percent V is at 100 F. Inc TAN Metal Wt. Change:

Cu. Mg, crn Fe, Al, Mg, Ag SOD pb Corr. mg./in.

325 F./1 hr 375 F./5 hr Lubricating Oil Blend Composition, Wt. percent:

Acryloid B s, cs., 40 F Total Acid No. (ASTMD-664).. SOD Lead Corrosionon 0 090 139 9:99 953 5: v

mww ro 00010.10 ovw o l V 10.20:: HOOD H00 00 0| I I |1| TABLEI-Continuecl Lubricating Oil Blend Blend 1 Blend .T Blend K Blend NOxidation-Corrosion Test 400 F./72 hr. 400 F./72 hr. 425 F./72 hr. 400F./48 hr. 425 F./48 hr.

Metal Wt. Change, mgJsq. crn.:

Cu 0. 22 0. 55 +0.02 +0.07 -0. 09 Fe, Al, Mg, Ag 0.0 0. 1512-0. 06 0.0t0+0. l6 0. 0 t0+0. 31 -0. 02 to 0. 04 100 F. Viscosity Increase,percent 9.2 10.1 5. 8 5. 6 TAN Increase 2. 8 2, 65 5. 39 4. 79 1- 36Sludge, g./100 ml. oil 0.0250 0.0339 0.0887

Blend B and Blend E which correspond to the improved syntheticlubricating oil compositions of the invention possess excellent extremepressure properties and outstanding anti-corrosive properties withrespect to copper and lead metals. Blend A Which is a synthetic fluidcontaining dimer acid is very poor with respect to its corrosiveness ofboth copper and lead metals and fails these tests by a wide margin.

Blend D and Blend E were prepared using a different base fluid fromBlends A, B and C. Blend E representative of a variation of thisinvention has excellent E.P. properties and outstanding corrosioninhibiting properties. The anti-corrosiveness toward lead as shown inthe Lead Washing Test conducted for a period of 336 hours isparticularly outstanding.

It is seen from the table that the additives from Examples 1, 2 and 3permitted formulation of products resistant to corrosion of metalsemployed in the construction of jet engines, especially copper andmagnesium which are susceptible to oxidative corrosion.

Repeatability and reproducibility of load-carrying determinations in theRyder Gear Test can be substantially affected by batch to batch and gearto gear variation in metallurgy, hardness and machining. It has beenfound that a comparative rating system, wherein the test oil is run onone side of a test gear and the reference oil is run on the reversefaces of the gear teeth, greatly improves precision and accuracy of testfluid evaluations.

This comparative rating from this back-to-back test method is expressedin percentage units:

parative rating:

Test Oil Rating, i Reference Oil Ratin x 100% The comparative referenceoil may be the standard Ryder Reference Oil B (a grade 1100 mineraloil), product formulation or a synthetic base fluid.

fore, only such'limitations should be imposed as are indicated in theappended claims.

We claim:

1. A synthetic lubricating oil composition comprising a major portion ofan aliphatic carboxylic acid ester having lubricating properties and amon-oamide of an heterocyclic aromatic amine selected from the groupconsisting of aminopyridines, dipyridylamines and phenothiazines and amaterial consisting essentially of trimer acids produced by thecondensation of unsaturated monocarboxylic acids having between 12 and22 carbon atoms per molecule in an amount suflicient to impart extremepressure properties to said lubricating oil composition.

2. A synthetic lubricating oil composition according to claim 1containing about 0.01 to 1.0 weight percent of said monoamide based onsaid lubricating oil composition.

3. A synthetic lubricating oil composition according to claim 1 in whichsaid unsaturated monocarboxylic acid has about 18 carbon atoms in thechain.

4. A synthetic lubricating oil composition according to claim 1containing from about 0.05 to 0.2 weight percent of said monoamide.

5. A synthetic lubricating oil composition according to claim 4containing the monoamide of 2-amino-pyridine and the trimer of linoleicacid.

6. A synthetic lubricating oil composition according to claim 4containing the monoamide of phenothiazine and the trimer of linoleicacid.

7. A synthetic lubricating oil composition comprising a major portion ofan aliphatic carboxylic acid ester having lubricating propertiescontaining 0.01 to 1.0 weight percent of a monoamide of a heterocyclicaromatic amine selected from the group consisting of aminopyridines,dipyridylamines and phenothiazines and a material consisting essentiallyof trimer acids produced by the condensation of unsaturatedmonocarboxylic acids having TABLE II.-COMPARATIVE LOAD CARRYING RATINGS(Back-to-back Ryder gear test method] These data show the effectivenessof the trimer acid monoamide of this invention for improving the loadcarrying capacities of typical base fluids, whereas a typicalantioxidant was without any beneficial effect.

Obviously, other modifications and variations of the invention ashereinbefore set forth may be made without between 12 and 22 carbonatoms per molecule, 0.1 to 2 weight percent of a compound selected fromthe group consisting of orthothiazine, metathiazine, parathiazine, andphenothiazine, 0.1 to 4.0 weight percent of a compound selected from theclass consisting of naphthylamine, phenyl-ot-naphthylamine,diphenylamine, phenyldeparting from the spirit and scope thereof, andthereenediamine, and 0.01 to 0.5 weight percent of a compound selectedfrom the class consisting of quinizarin, ali- Zarin, purpurxanthrene,anthrarufin and chrysazin.

8. A synthetic lubricating oil according to claim 7 containing 0.0001 to0.1 Weight percent of sebacic acid.

9. A synthetic lubricating oil composition according to claim 7 in whichsaid unsaturated monooarboxylic acid is about 18 carbon atoms.

10. A synthetic lubricating oil composition according to claim 7containing from about 0.05 to 0.2 weight percent of said monoamide.

11. A synthetic lubricating oil composition according to claim 7containing the monoarnide of Z-aminopyridine and the trimer of linoleicacid.

12. A synthetic lubricating oil according to claim 7 containing themonoamide of phenothiazine and the trirner of linoleic acid.

13. A synthetic lubricating oil composition comprising a major portionof an aliphatic carboxylic acid ester having lubricating propertiescontaining 0.05 to 0.2. weight percent of a mon'oamide ofZ-aminopyridine and the UNITED STATES PATENTS 2,718,503 9/1955 Rocchini252-515 2,948,598 8/1960 Brehm 25251.5 X 3,247,111 4/1966 Oberright etal. 25251.5 X 3,256,196 6/1966 Eickemeyer et al. 25251.5

OTHER REFERENCES Barnes et al., Synthetic Ester Lubricants, LubricationEngineering, August 1957, pp. 454-458.

DANIEL E. WYMAN, Primary Examin r.

P. P. GARV'IN, Assistant Examiner.

1. A SYNTHETIC LUBRICATING OIL COMPOSITION COMPRISING A MAJOR PORTION OFAN ALIPHATIC CARBOXYLIC ACID ESTER HAVING LUBRICATING PROPERTIES AND AMONOAMIDE OF AN HETEROCYCLIC AROMATIC AMINE SELECTED FROM THE GROUPCONSISTING OF AMINOPYRIDINES, DIPYRIDYLAMINES AND PHENOTHIZINES AND AMATERIAL CONSISTING ESSENTIALLY OF TRIMER ACIDS PRODUCED BY THECONDENSATION OF UNSATURATED MONOCARBOXYLIC ACIDS HAVING BETWEEN 12 TO 22CARBON ATOMS PER MOLECULE IN AN AMOUNT SUFFICIENT TO IMPART EXTREMEPRESSURE PROPERTIES TO SAID LUBRICATING OIL COMPOSITION.